libjava/classpath/javax/swing/JPopupMenu.java

   1 /* JPopupMenu.java --
   2    Copyright (C) 2002, 2004, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package javax.swing;
  40
  41 import java.awt.Component;
  42 import java.awt.Dimension;
  43 import java.awt.Insets;
  44 import java.awt.Point;
  45 import java.awt.event.KeyEvent;
  46 import java.awt.event.MouseEvent;
  47 import java.beans.PropertyChangeEvent;
  48 import java.beans.PropertyChangeListener;
  49 import java.util.ArrayList;
  50 import java.util.EventListener;
  51
  52 import javax.accessibility.Accessible;
  53 import javax.accessibility.AccessibleContext;
  54 import javax.accessibility.AccessibleRole;
  55 import javax.swing.event.PopupMenuEvent;
  56 import javax.swing.event.PopupMenuListener;
  57 import javax.swing.plaf.PopupMenuUI;
  58
  59 /**
  60  * JPopupMenu is a container that is used to display popup menu's menu
  61  * items. By default JPopupMenu is a lightweight container, however if it
  62  * is the case that JPopupMenu's bounds are outside of main window, then
  63  * heawyweight container will be used to display menu items. It is also
  64  * possible to change JPopupMenu's default  behavior and set JPopupMenu
  65  * to always use heavyweight container.
  66  *
  67  * JPopupMenu can be displayed anywhere; it is a floating free popup menu.
  68  * However before JPopupMenu is diplayed, its invoker property should be set.
  69  * JPopupMenu's invoker is a component relative to which popup menu is
  70  * displayed.
  71  *
  72  * JPopupMenu fires PopupMenuEvents to its registered listeners. Whenever
  73  * JPopupMenu becomes visible on the screen then PopupMenuEvent indicating
  74  * that popup menu became visible will be fired. In the case when
  75  * JPopupMenu becomes invisible or cancelled without selection, then
  76  * popupMenuBecomeInvisible() or popupMenuCancelled() methods of
  77  * PopupMenuListeners will be invoked.
  78  *
  79  * JPopupMenu also fires PropertyChangeEvents when its bound properties
  80  * change.In addittion to inheritted bound properties, JPopupMenu has
  81  * 'visible' bound property. When JPopupMenu becomes visible/invisible on
  82  * the screen it fires PropertyChangeEvents to its registered
  83  * PropertyChangeListeners.
  84  */
  85 public class JPopupMenu extends JComponent implements Accessible, MenuElement
  86 {
  87   private static final long serialVersionUID = -8336996630009646009L;
  88
  89   /* indicates if popup's menu border should be painted*/
  90   private boolean borderPainted = true;
  91
  92   /** Flag indicating whether lightweight, mediumweight or heavyweight popup
  93      is used to display menu items.
  94
  95      These are the possible cases:
  96
  97      1. if DefaultLightWeightPopupEnabled true
  98          (i)  use lightweight container if popup feets inside top-level window
  99          (ii) only use heavyweight container (JDialog) if popup doesn't fit.
 100
 101      2. if DefaultLightWeightPopupEnabled false
 102          (i) if popup fits, use awt.Panel (mediumWeight)
 103          (ii) if popup doesn't fit, use JDialog (heavyWeight)
 104   */
 105   private static boolean DefaultLightWeightPopupEnabled = true;
 106
 107   /* Component that invokes popup menu. */
 108   transient Component invoker;
 109
 110   /* Label for this popup menu. It is not used in most of the look and feel themes. */
 111   private String label;
 112
 113   /*Amount of space between menuItem's in JPopupMenu and JPopupMenu's border */
 114   private Insets margin;
 115
 116   /** Indicates whether ligthWeight container can be used to display popup
 117      menu. This flag is the same as DefaultLightWeightPopupEnabled, but setting
 118      this flag can change popup menu after creation of the object */
 119   private boolean lightWeightPopupEnabled;
 120
 121   /** SelectionModel that keeps track of menu selection. */
 122   private SingleSelectionModel selectionModel;
 123
 124   /* Popup that is used to display JPopupMenu */
 125   private transient Popup popup;
 126
 127   /**
 128    * Location of the popup, X coordinate.
 129    */
 130   private int popupLocationX;
 131
 132   /**
 133    * Location of the popup, Y coordinate.
 134    */
 135   private int popupLocationY;
 136
 137   /* Field indicating if popup menu is visible or not */
 138   private boolean visible = false;
 139
 140   /**
 141    * Creates a new JPopupMenu object.
 142    */
 143   public JPopupMenu()
 144   {
 145     this(null);
 146   }
 147
 148   /**
 149    * Creates a new JPopupMenu with specified label
 150    *
 151    * @param label Label for popup menu.
 152    */
 153   public JPopupMenu(String label)
 154   {
 155     lightWeightPopupEnabled = getDefaultLightWeightPopupEnabled();
 156     setLabel(label);
 157     setSelectionModel(new DefaultSingleSelectionModel());
 158     super.setVisible(false);
 159     updateUI();
 160   }
 161
 162   /**
 163   * Adds given menu item to the popup menu
 164   *
 165   * @param item menu item to add to the popup menu
 166   *
 167   * @return menu item that was added to the popup menu
 168   */
 169   public JMenuItem add(JMenuItem item)
 170   {
 171     this.insert(item, -1);
 172     return item;
 173   }
 174
 175   /**
 176    * Constructs menu item with a specified label and adds it to
 177    * popup menu
 178    *
 179    * @param text label for the menu item to be added
 180    *
 181    * @return constructed menu item that was added to the popup menu
 182    */
 183   public JMenuItem add(String text)
 184   {
 185     JMenuItem item = new JMenuItem(text);
 186     return add(item);
 187   }
 188
 189   /**
 190    * Constructs menu item associated with the specified action
 191    * and adds it to the popup menu
 192    *
 193    * @param action Action for the new menu item
 194    *
 195    * @return menu item that was added to the menu
 196    */
 197   public JMenuItem add(Action action)
 198   {
 199     JMenuItem item = createActionComponent(action);
 200
 201     if (action != null)
 202       action.addPropertyChangeListener(createActionChangeListener(item));
 203
 204     return add(item);
 205   }
 206
 207   /**
 208    * Revomes component at the given index from the menu.
 209    *
 210    * @param index index of the component that will be removed in the menu
 211    */
 212   public void remove(int index)
 213   {
 214     super.remove(index);
 215     revalidate();
 216   }
 217
 218   /**
 219    * Create menu item associated with the given action
 220    * and inserts it into the popup menu at the specified index
 221    *
 222    * @param action Action for the new menu item
 223    * @param index index in the popup menu at which to insert new menu item.
 224    */
 225   public void insert(Action action, int index)
 226   {
 227     JMenuItem item = new JMenuItem(action);
 228     this.insert(item, index);
 229   }
 230
 231   /**
 232    * Insert given component to the popup menu at the
 233    * specified index
 234    *
 235    * @param component Component to insert
 236    * @param index Index at which to insert given component
 237    */
 238   public void insert(Component component, int index)
 239   {
 240     super.add(component, index);
 241   }
 242
 243   /**
 244    * Returns flag indicating if newly created JPopupMenu will use
 245    * heavyweight or lightweight container to display its menu items
 246    *
 247    * @return true if JPopupMenu will use lightweight container to display
 248    * menu items by default, and false otherwise.
 249    */
 250   public static boolean getDefaultLightWeightPopupEnabled()
 251   {
 252     return DefaultLightWeightPopupEnabled;
 253   }
 254
 255   /**
 256    * Sets whether JPopupMenu should use ligthWeight container to
 257    * display it menu items by default
 258    *
 259    * @param enabled true if JPopupMenu should use lightweight container
 260    * for displaying its menu items, and false otherwise.
 261    */
 262   public static void setDefaultLightWeightPopupEnabled(boolean enabled)
 263   {
 264     DefaultLightWeightPopupEnabled = enabled;
 265   }
 266
 267   /**
 268    * This method returns the UI used to display the JPopupMenu.
 269    *
 270    * @return The UI used to display the JPopupMenu.
 271    */
 272   public PopupMenuUI getUI()
 273   {
 274     return (PopupMenuUI) ui;
 275   }
 276
 277   /**
 278    * Set the "UI" property of the menu item, which is a look and feel class
 279    * responsible for handling popupMenu's input events and painting it.
 280    *
 281    * @param ui The new "UI" property
 282    */
 283   public void setUI(PopupMenuUI ui)
 284   {
 285     super.setUI(ui);
 286   }
 287
 288   /**
 289    * This method sets this menuItem's UI to the UIManager's default for the
 290    * current look and feel.
 291    */
 292   public void updateUI()
 293   {
 294     setUI((PopupMenuUI) UIManager.getUI(this));
 295     invalidate();
 296   }
 297
 298   /**
 299    * This method returns a name to identify which look and feel class will be
 300    * the UI delegate for the menuItem.
 301    *
 302    * @return The Look and Feel classID. "PopupMenuUI"
 303    */
 304   public String getUIClassID()
 305   {
 306     return "PopupMenuUI";
 307   }
 308
 309   /**
 310    * Returns selectionModel used by this popup menu to keep
 311    * track of the selection.
 312    *
 313    * @return popup menu's selection model
 314    */
 315   public SingleSelectionModel getSelectionModel()
 316   {
 317     return selectionModel;
 318   }
 319
 320   /**
 321    * Sets selection model for this popup menu
 322    *
 323    * @param model new selection model of this popup menu
 324    */
 325   public void setSelectionModel(SingleSelectionModel model)
 326   {
 327         selectionModel = model;
 328   }
 329
 330   /**
 331    * Creates new menu item associated with a given action.
 332    *
 333    * @param action Action used to create new menu item
 334    *
 335    * @return new created menu item associated with a given action.
 336    */
 337   protected JMenuItem createActionComponent(Action action)
 338   {
 339     return new JMenuItem(action);
 340   }
 341
 342   /**
 343    * Creates PropertyChangeListener that listens to PropertyChangeEvents
 344    * occuring in the Action associated with given menu item in this popup menu.
 345    *
 346    * @param item MenuItem
 347    *
 348    * @return The PropertyChangeListener
 349    */
 350   protected PropertyChangeListener createActionChangeListener(JMenuItem item)
 351   {
 352     return new ActionChangeListener();
 353   }
 354
 355   /**
 356    * Returns true if this popup menu will display its menu item in
 357    * a lightweight container and false otherwise.
 358    *
 359    * @return true if this popup menu will display its menu items
 360    * in a lightweight container and false otherwise.
 361    */
 362   public boolean isLightWeightPopupEnabled()
 363   {
 364     return lightWeightPopupEnabled;
 365   }
 366
 367   /**
 368    * DOCUMENT ME!
 369    *
 370    * @param enabled DOCUMENT ME!
 371    */
 372   public void setLightWeightPopupEnabled(boolean enabled)
 373   {
 374     lightWeightPopupEnabled = enabled;
 375   }
 376
 377   /**
 378    * Returns label for this popup menu
 379    *
 380    * @return label for this popup menu
 381    */
 382   public String getLabel()
 383   {
 384     return label;
 385   }
 386
 387   /**
 388    * Sets label for this popup menu. This method fires PropertyChangeEvent
 389    * when the label property is changed. Please note that most
 390    * of the Look &amp; Feel will ignore this property.
 391    *
 392    * @param label label for this popup menu
 393    */
 394   public void setLabel(String label)
 395   {
 396     if (label != this.label)
 397       {
 398         String oldLabel = this.label;
 399         this.label = label;
 400         firePropertyChange("label", oldLabel, label);
 401       }
 402   }
 403
 404   /**
 405    * Adds separator to this popup menu
 406    */
 407   public void addSeparator()
 408   {
 409     // insert separator at the end of the list of menu items
 410     this.insert(new Separator(), -1);
 411   }
 412
 413   /**
 414    * Adds popupMenuListener to listen for PopupMenuEvents fired
 415    * by the JPopupMenu
 416    *
 417    * @param listener PopupMenuListener to add to JPopupMenu
 418    */
 419   public void addPopupMenuListener(PopupMenuListener listener)
 420   {
 421     listenerList.add(PopupMenuListener.class, listener);
 422   }
 423
 424   /**
 425    * Removes PopupMenuListener from JPopupMenu's list of listeners
 426    *
 427    * @param listener PopupMenuListener which needs to be removed
 428    */
 429   public void removePopupMenuListener(PopupMenuListener listener)
 430   {
 431     listenerList.remove(PopupMenuListener.class, listener);
 432   }
 433
 434   /**
 435    * Returns array of PopupMenuListeners that are listening to JPopupMenu
 436    *
 437    * @return Array of PopupMenuListeners that are listening to JPopupMenu
 438    */
 439   public PopupMenuListener[] getPopupMenuListeners()
 440   {
 441     return ((PopupMenuListener[]) listenerList.getListeners(PopupMenuListener.class));
 442   }
 443
 444   /**
 445    * This method calls popupMenuWillBecomeVisible() of popup menu's
 446    * PopupMenuListeners. This method is invoked just before popup menu
 447    * will appear on the screen.
 448    */
 449   protected void firePopupMenuWillBecomeVisible()
 450   {
 451     EventListener[] ll = listenerList.getListeners(PopupMenuListener.class);
 452
 453     for (int i = 0; i < ll.length; i++)
 454       ((PopupMenuListener) ll[i]).popupMenuWillBecomeVisible(new PopupMenuEvent(this));
 455   }
 456
 457   /**
 458    * This method calls popupMenuWillBecomeInvisible() of popup
 459    * menu's PopupMenuListeners. This method is invoked just before popup
 460    * menu will disappear from the screen
 461    */
 462   protected void firePopupMenuWillBecomeInvisible()
 463   {
 464     EventListener[] ll = listenerList.getListeners(PopupMenuListener.class);
 465
 466     for (int i = 0; i < ll.length; i++)
 467       ((PopupMenuListener) ll[i]).popupMenuWillBecomeInvisible(new PopupMenuEvent(this));
 468   }
 469
 470   /**
 471    * This method calls popupMenuCanceled() of popup menu's PopupMenuListeners.
 472    * This method is invoked just before popup menu is cancelled. This happens
 473    * when popup menu is closed without selecting any of its menu items. This
 474    * usually happens when the top-level window is resized or moved.
 475    */
 476   protected void firePopupMenuCanceled()
 477   {
 478     EventListener[] ll = listenerList.getListeners(PopupMenuListener.class);
 479
 480     for (int i = 0; i < ll.length; i++)
 481       ((PopupMenuListener) ll[i]).popupMenuCanceled(new PopupMenuEvent(this));
 482   }
 483
 484   /**
 485    * This methods sets popup menu's size to its' preferred size. If the
 486    * popup menu's size is previously set it will be ignored.
 487    */
 488   public void pack()
 489   {
 490     // Hook up this call so that it gets executed on the event thread in order
 491     // to avoid synchronization problems when calling the layout manager.
 492     if (! SwingUtilities.isEventDispatchThread())
 493       {
 494         SwingUtilities.invokeLater(new Runnable()
 495           {
 496             public void run()
 497             {
 498               show();
 499             }
 500           });
 501       }
 502
 503     setSize(getPreferredSize());
 504   }
 505
 506   /**
 507    * Return visibility of the popup menu
 508    *
 509    * @return true if popup menu is visible on the screen and false otherwise.
 510    */
 511   public boolean isVisible()
 512   {
 513     return visible;
 514   }
 515
 516   /**
 517    * Sets visibility property of this popup menu. If the property is
 518    * set to true then popup menu will be dispayed and popup menu will
 519    * hide itself if visible property is set to false.
 520    *
 521    * @param visible true if popup menu will become visible and false otherwise.
 522    */
 523   public void setVisible(final boolean visible)
 524   {
 525     // Hook up this call so that it gets executed on the event thread in order
 526     // to avoid synchronization problems when calling the layout manager.
 527     if (! SwingUtilities.isEventDispatchThread())
 528       {
 529         SwingUtilities.invokeLater(new Runnable()
 530           {
 531             public void run()
 532             {
 533               setVisible(visible);
 534             }
 535           });
 536       }
 537
 538     if (visible == isVisible())
 539       return;
 540
 541     boolean old = isVisible();
 542     this.visible = visible;
 543     if (old != isVisible())
 544       {
 545         firePropertyChange("visible", old, isVisible());
 546         if (visible)
 547           {
 548             firePopupMenuWillBecomeVisible();
 549
 550             PopupFactory pf = PopupFactory.getSharedInstance();
 551             pack();
 552             popup = pf.getPopup(invoker, this, popupLocationX, popupLocationY);
 553             popup.show();
 554           }
 555         else
 556           {
 557             firePopupMenuWillBecomeInvisible();
 558             popup.hide();
 559           }
 560       }
 561   }
 562
 563   /**
 564    * Sets location of the popup menu.
 565    *
 566    * @param x X coordinate of the popup menu's location
 567    * @param y Y coordinate of the popup menu's location
 568    */
 569   public void setLocation(int x, int y)
 570   {
 571     popupLocationX = x;
 572     popupLocationY = y;
 573     // Handle the case when the popup is already showing. In this case we need
 574     // to fetch a new popup from PopupFactory and use this. See the general
 575     // contract of the PopupFactory.
 576   }
 577
 578   /**
 579    * Returns popup menu's invoker.
 580    *
 581    * @return popup menu's invoker
 582    */
 583   public Component getInvoker()
 584   {
 585     return invoker;
 586   }
 587
 588   /**
 589    * Sets popup menu's invoker.
 590    *
 591    * @param component The new invoker of this popup menu
 592    */
 593   public void setInvoker(Component component)
 594   {
 595     invoker = component;
 596   }
 597
 598   /**
 599    * This method displays JPopupMenu on the screen at the specified
 600    * location. Note that x and y coordinates given to this method
 601    * should be expressed in terms of the popup menus' invoker.
 602    *
 603    * @param component Invoker for this popup menu
 604    * @param x x-coordinate of the popup menu relative to the specified invoker
 605    * @param y y-coordiate of the popup menu relative to the specified invoker
 606    */
 607   public void show(Component component, int x, int y)
 608   {
 609     if (component.isShowing())
 610       {
 611         setInvoker(component);
 612         Point p = new Point(x, y);
 613         SwingUtilities.convertPointToScreen(p, component);
 614         setLocation(p.x, p.y);
 615         setVisible(true);
 616       }
 617   }
 618
 619   /**
 620    * Returns component located at the specified index in the popup menu
 621    *
 622    * @param index index of the component to return
 623    *
 624    * @return component located at the specified index in the popup menu
 625    *
 626    * @deprecated Replaced by getComponent(int)
 627    */
 628   public Component getComponentAtIndex(int index)
 629   {
 630     return getComponent(index);
 631   }
 632
 633   /**
 634    * Returns index of the specified component in the popup menu
 635    *
 636    * @param component Component to look for
 637    *
 638    * @return index of the specified component in the popup menu
 639    */
 640   public int getComponentIndex(Component component)
 641   {
 642     Component[] items = getComponents();
 643
 644     for (int i = 0; i < items.length; i++)
 645       {
 646         if (items[i].equals(component))
 647           return i;
 648       }
 649
 650     return -1;
 651   }
 652
 653   /**
 654    * Sets size of the popup
 655    *
 656    * @param size Dimensions representing new size of the popup menu
 657    */
 658   public void setPopupSize(Dimension size)
 659   {
 660     super.setSize(size);
 661   }
 662
 663   /**
 664    * Sets size of the popup menu
 665    *
 666    * @param width width for the new size
 667    * @param height height for the new size
 668    */
 669   public void setPopupSize(int width, int height)
 670   {
 671     super.setSize(width, height);
 672   }
 673
 674   /**
 675    * Selects specified component in this popup menu.
 676    *
 677    * @param selected component to select
 678    */
 679   public void setSelected(Component selected)
 680   {
 681     int index = getComponentIndex(selected);
 682     selectionModel.setSelectedIndex(index);
 683   }
 684
 685   /**
 686    * Checks if this popup menu paints its border.
 687    *
 688    * @return true if this popup menu paints its border and false otherwise.
 689    */
 690   public boolean isBorderPainted()
 691   {
 692     return borderPainted;
 693   }
 694
 695   /**
 696    * Sets if the border of the popup menu should be
 697    * painter or not.
 698    *
 699    * @param painted true if the border should be painted and false otherwise
 700    */
 701   public void setBorderPainted(boolean painted)
 702   {
 703     borderPainted = painted;
 704   }
 705
 706   /**
 707    * Returns margin for this popup menu.
 708    *
 709    * @return margin for this popup menu.
 710    */
 711   public Insets getMargin()
 712   {
 713     return margin;
 714   }
 715
 716   /**
 717    * A string that describes this JPopupMenu. Normally only used
 718    * for debugging.
 719    *
 720    * @return A string describing this JMenuItem
 721    */
 722   protected String paramString()
 723   {
 724     StringBuffer sb = new StringBuffer();
 725     sb.append(super.paramString());
 726     sb.append(",label=");
 727     if (getLabel() != null)
 728       sb.append(getLabel());
 729     sb.append(",lightWeightPopupEnabled=").append(isLightWeightPopupEnabled());
 730     sb.append(",margin=");
 731     if (getMargin() != null)
 732       sb.append(margin);
 733     sb.append(",paintBorder=").append(isBorderPainted());
 734     return sb.toString();
 735   }
 736
 737   /**
 738   * Process mouse events forwarded from MenuSelectionManager. This method
 739   * doesn't do anything. It is here to conform to the MenuElement interface.
 740   *
 741   * @param event event forwarded from MenuSelectionManager
 742   * @param path path to the menu element from which event was generated
 743   * @param manager MenuSelectionManager for the current menu hierarchy
 744   */
 745   public void processMouseEvent(MouseEvent event, MenuElement[] path,
 746                                 MenuSelectionManager manager)
 747   {
 748     // Empty Implementation. This method is needed for the implementation
 749     // of MenuElement interface
 750   }
 751
 752   /**
 753    * Process key events forwarded from MenuSelectionManager. This method
 754    * doesn't do anything. It is here to conform to the MenuElement interface.
 755    *
 756    * @param event event forwarded from MenuSelectionManager
 757    * @param path path to the menu element from which event was generated
 758    * @param manager MenuSelectionManager for the current menu hierarchy
 759    *
 760    */
 761   public void processKeyEvent(KeyEvent event, MenuElement[] path,
 762                               MenuSelectionManager manager)
 763   {
 764     // Empty Implementation. This method is needed for the implementation
 765     // of MenuElement interface
 766   }
 767
 768   /**
 769    * Method of MenuElement Interface. It is invoked when
 770    * popupMenu's selection has changed
 771    *
 772    * @param changed true if this popupMenu is part of current menu
 773    * hierarchy and false otherwise.
 774    */
 775   public void menuSelectionChanged(boolean changed)
 776   {
 777     if (! changed)
 778       setVisible(false);
 779   }
 780
 781   /**
 782    * Return subcomonents of this popup menu. This method returns only
 783    * components that implement the <code>MenuElement</code> interface.
 784    *
 785    * @return array of menu items belonging to this popup menu
 786    */
 787   public MenuElement[] getSubElements()
 788   {
 789     Component[] items = getComponents();
 790     ArrayList subElements = new ArrayList();
 791
 792     for (int i = 0; i < items.length; i++)
 793       if (items[i] instanceof MenuElement)
 794         subElements.add(items[i]);
 795
 796     return (MenuElement[])
 797       subElements.toArray(new MenuElement[subElements.size()]);
 798   }
 799
 800   /**
 801    * Method of the MenuElement interface. Returns reference to itself.
 802    *
 803    * @return Returns reference to itself
 804    */
 805   public Component getComponent()
 806   {
 807     return this;
 808   }
 809
 810   /**
 811    * Checks if observing mouse event should trigger popup
 812    * menu to show on the screen.
 813    *
 814    * @param event MouseEvent to check
 815    *
 816    * @return true if the observing mouse event is popup trigger and false otherwise
 817    */
 818   public boolean isPopupTrigger(MouseEvent event)
 819   {
 820     return ((PopupMenuUI) getUI()).isPopupTrigger(event);
 821   }
 822
 823   /**
 824    * DOCUMENT ME!
 825    *
 826    * @return DOCUMENT ME!
 827    */
 828   public AccessibleContext getAccessibleContext()
 829   {
 830     if (accessibleContext == null)
 831       accessibleContext = new AccessibleJPopupMenu();
 832
 833     return accessibleContext;
 834   }
 835
 836   /**
 837    * This is the separator that can be used in popup menu.
 838    */
 839   public static class Separator extends JSeparator
 840   {
 841     public Separator()
 842     {
 843       super();
 844     }
 845
 846     public String getUIClassID()
 847     {
 848       return "PopupMenuSeparatorUI";
 849     }
 850   }
 851
 852   protected class AccessibleJPopupMenu extends AccessibleJComponent
 853   {
 854     private static final long serialVersionUID = 7423261328879849768L;
 855
 856     protected AccessibleJPopupMenu()
 857     {
 858       // Nothing to do here.
 859     }
 860
 861     public AccessibleRole getAccessibleRole()
 862     {
 863       return AccessibleRole.POPUP_MENU;
 864     }
 865   }
 866
 867   /* This class resizes popup menu and repaints popup menu appropriately if one
 868    of item's action has changed */
 869   private class ActionChangeListener implements PropertyChangeListener
 870   {
 871     public void propertyChange(PropertyChangeEvent evt)
 872     {
 873       // We used to have a revalidate() and repaint() call here. However I think
 874       // this is not needed. Instead, a new Popup has to be fetched from the
 875       // PopupFactory and used here.
 876     }
 877   }
 878 }